Information outputting apparatus, information reporting method and information signal supply route selecting method

ABSTRACT

The present invention presents an information-outputting apparatus, an information-reporting method and an information-signal-supply-route-selecting method, which provide a digital-content utilization environment giving the user a high degree of freedom to make use of the apparatus and the methods. 
     The information-outputting apparatus receives an isochronous packet transmitted by a source external apparatus by adoption of an isochronous communication method through a digital bus connecting the external apparatus to the information-outputting apparatus. In the information-outputting apparatus, an IEEE 1394 I/F circuit extracts information on the source electronic apparatus and information on the transmission format. A control unit supplies these pieces of information to an OSD-generating circuit for displaying them on a screen of a display unit employed in the information-outputting apparatus.

BACKGROUND OF THE INVENTION

The present invention relates to an information-outputting apparatussuch as a monitor apparatus connected to a network connected to aplurality of electronic apparatuses through digital buses eachconforming to typically the IEEE 1394 standard, an information-reportingmethod for informing the user of information on a content to be outputby the information-outputting apparatus and aninformation-signal-supply-route-selecting method in the network.

In recent years, a variety of digital contents are abundantly providedby way of communication media such as broadcasting media and theInternet as well as through recording media such as a DVD (digital videodisc). It is conceivably possible to widen the range of applications ofsuch abundantly available digital contents and to well provide anenvironment of utilizing digital contents wherein the user has a highdegree of freedom to use the contents.

It is also conceivably possible to provide a digital interface to eachof a variety of digital apparatuses such as digital-content playback andrecording apparatuses. By providing a digital interface to each of avariety of digital apparatuses as such, a digital content can betransmitted at a high speed and copied as well as played back withoutdegrading the quality.

While there are a variety of digital interfaces, a digital interfaceconforming to the IEEE 1394 standard draws much attention. The IEEE 1394digital interface is capable of transmitting a digital content at a highspeed and protecting a copyright of a digital content with a high degreeof reliability. To be more specific, the digital interface conforming tothe IEEE 1394 standard is capable of transmitting signals such asdigital video and audio signals, which must satisfy real-timerequirements.

In addition, in a communication through a digital interface conformingto the IEEE 1394 standard between an electronic apparatus serving of asource of a digital content and an electronic apparatus serving as arecipient of the digital content, by adding information on copy controlto the digital content, the apparatus transmitting the digital contentis capable of determining whether or not to give the recipient apparatusa right to copy the digital content.

The electronic apparatus serving of a source of a digital contentencrypts the digital content to be transmitted. If the electronicapparatus serving as a recipient of a digital content is treated as anapparatus not allowed to copy the digital content by adding informationon copy control to the digital content, the recipient apparatus is notinformed of an encryption key information for decrypting the encrypteddigital content so that a copyright of the digital content can beprotected with a high degree of reliability.

By the way, digital television broadcasting presenting digital contentsthrough broadcasting media is already under way. It is thus conceivablypossible to provide a digital monitor apparatus or a digital televisionreceiver that has a function for receiving a digital televisionbroadcast. In the digital television broadcasting, digital data istypically data comprising a plurality of broadcasted programs. Prior tobroadcasting, the data is subjected to compression adopting an MPEGmethod and multiplexing. Thus, the digital monitor apparatus must havean MPEG decoder.

By providing a digital interface to a digital monitor apparatus havingan MPEG decoder, a digital content completing an encoding processadopting the MPEG method can be supplied to the apparatus as it is. Thedigital monitor apparatus is capable of decoding and playing back thedigital content. Thus, a digital interface provided to a digital monitorapparatus is conceivable.

By merely providing a digital monitor apparatus with a digitalinterface, however, a problem arises in some cases. That is to say,while a digital monitor apparatus having a digital interface can beconnected to a digital VTR, a hard-disc drive and the so-calledcamcoder, which is equipment comprising a video camera and a VTR builtinto a single body, a video signal stored in a recording medium such asa video tape by a digital VTR or a camcoder is in some cases a DV(Digital Video) signal obtained as a result of data compression based ona DV method instead of a signal encoded by adopting the MPEG method.

The DV method is a home digital VTR standard set by an HD DigitalConference, which was established by such as manufacturers of digitalequipment as promoters. In accordance with the DV method, a DV signal isobtained as a result of compressing data of a video signal in frameunits. That is to say, a DV signal consists of only I (Intra) picturecomponents in the so-called MPEG method. An I picture is a pictureobtained as a result of a intra-frame encoding process.

Thus, a digital monitor apparatus having only an MPEG decoder is notcapable of decoding and playing back a DV signal supplied thereto by adigital VTR or the so-called camcoder by way of the digital interface.

Assuming that a digital monitor apparatus 1 having an analog inputterminal in addition to an MPEG decoder and a digital interface isconnected to a DV storage 2 of typically a digital VTR, an MPEG-TS(Transport Stream) storage 3 of typically a hard disc and a DV camcoder4 as shown in FIG. 1.

In FIG. 1, solid lines 5, 6 and 7 each represent a digital signal cablewhereas dashed lines 8, 9 and 10 each represent an analog signal cable.That is to say, the digital monitor apparatus 1 is connected to the DVstorage 2, the MPEG-TS storage 3 and the DV camcoder 4 by the analogsignal cables 8, 9 and 10 respectively and to the DV storage 2 by thedigital signal cable 5, whereas the DV storage 2 is connected by thedigital signal cable 6 to the MPEG-TS storage 3 which is connected tothe DV camcoder 4 by the digital signal cable 7 to form a network.

It should be noted that the MPEG-TS storage 3 is an apparatus used for,among others, storing and playing back an MPEG-TS signal, which isobtained as a result of a process of multiplexing digital contents eachresulting from data compression adopting the MPEG method.

A content decoded by the DV storage 2, the MPEG-TS storage 3 or the DVcamcoder 4 into an analog signal is supplied to the digital monitorapparatus 1 through the analog signal cable 8, 9 or 10 respectively. Inthis case, the video of the content is displayed on a screen G of thedigital monitor apparatus 1 as shown in FIG. 2A and the sound of thecontent is output by speakers SP1 and SP2 as is the case with theconventional apparatus.

By the same token, an MPEG-TS signal can be supplied from the MPEG-TSstorage 3 to the digital monitor apparatus 1 through the digital signalcables 6 and 5 as it is. In this case, since the digital monitorapparatus 1 has an MPEG decoder, the monitor apparatus 1 is capable ofdisplaying the video of the digital content on the screen G thereof asshown in FIG. 2A and outputting the sound of the content through thespeakers SP1 and SP2.

By the same token, a DV signal can be supplied to the digital monitorapparatus 1 from the DV storage 2 through the digital signal cable 5 orfrom the DV camcoder 4 through the digital signal cables 7, 6 and 5 asit is. In this case, however, since the digital monitor apparatus 1 doesnot have a DV decoder, the monitor apparatus 1 is not capable of playingback the DV signal. As a result, as a conceivable method, the digitalmonitor apparatus 1 is put in a mute state as typically shown in FIG. 2Bto prevent the video and the sound of the digital content from beingoutput as noises.

With such a method, however, the user is not capable of immediatelyknowing why the content the user is trying to watch and listen to is notplayed back. In addition, in the case of a network comprising aplurality of electronic apparatuses connected to each other as shown inFIG. 1, the user of the digital monitor apparatus 1 is not capable ofrecognizing which route is used for supplying a content to the monitorapparatus 1 from an external apparatus connected to the monitorapparatus 1 by the network.

In the case of the network shown in FIG. 1, for example, as describedabove, the digital monitor apparatus 1 serving as the core apparatus mayreceive 3 different kinds of contents, namely:

-   -   (1) a decodable and reproducible digital content;    -   (2) an undecodable digital content; and    -   (3) a content supplied as an analog signal.

If an undecodable digital content is inadvertently supplied to thedigital monitor apparatus 1, there may be raised a problem that theundecodable digital content is interpreted incorrectly as a failureoccurring in the monitor apparatus 1 or the apparatus generating thecontent. In addition, since a content may be supplied to the digitalmonitor apparatus 1 from the same electronic apparatus through an analogsignal cable or a digital signal cable, it is difficult to handlecontents in the information reporting and outputting system in somecases. Thus, the environment for utilizing a digital content cannot besaid to be sufficiently well provided yet.

SUMMARY OF THE INVENTION

The present invention presents an information-outputting apparatus, aninformation-reporting method and aninformation-signal-supply-route-selecting method, which provide adigital-content utilization environment giving the user a high degree offreedom to make use of the apparatus and the methods.

The information-outputting apparatus provided by the present inventionis an apparatus connected to a network comprising a plurality ofelectronic apparatuses connected to each other by digital buses. Theinformation-outputting apparatus comprises: a digital interface unit forreceiving a digital signal transmitted through one of the digital buses;information-detecting means for detecting source-apparatus informationindicating an electronic apparatus serving as a source outputting thedigital signal and information on a format of the digital signal fromthe digital signal, which is received through the digital interfaceunit; and information-reporting means for reporting the source-apparatusinformation and the information on the format, which are detected by theinformation-detecting means.

In the information-outputting apparatus described above,source-apparatus information and information on a format, which aretransmitted through a digital bus along with a main digital signal, aredetected by the information-detecting means and reported by theinformation-reporting means.

It is thus possible for the user to know which electronic apparatusconnected to a digital bus has supplied a digital signal and what formatthe digital signal has.

In addition, the information-outputting apparatus further hasinformation-tabularizing means for organizing source-apparatusinformation and information on a format, which are detected by theinformation-detecting means, for each of the electronic apparatusesconnected to the network in a table by associating the pair ofsource-apparatus information and information on a format with thecorresponding electronic apparatus, whereas the information-reportingmeans reports the information tabularized by theinformation-tabularizing means to the user.

In the information-outputting apparatus, the information-detecting meansdetects a source-apparatus number and information on a format for eachof the electronic apparatuses connected to the network. Then, theinformation-tabularizing means organizes the detected pieces ofinformation into a table by associating them with the correspondingelectronic apparatus. Finally, the information-reporting means reportssome or all of the information tabularized by theinformation-tabularizing means.

It is thus possible for the information-outputting apparatus to informthe user of the information-outputting apparatus of source-apparatusinformation and information on a format, which are each received as aninformation signal along with a main digital signal, and information onconnections of the other electronic apparatuses connected to thenetwork.

Furthermore, the information-outputting apparatus described above has:one or more base-band-signal input terminals each connected to one ofthe electronic apparatuses connected to the network and each used forreceiving a base-band signal generated by the electronic apparatus; andinformation-adding means for adding source-apparatus informationindicating a source apparatus generating a base-band signal andinformation, which indicates the format of the base-band signal in casethe base-band signal has been encoded, for each of the electronicapparatuses connected to the base-band-signal input terminals to theinformation tabularized by the information-tabularizing means byassociating the source-apparatus information with the informationindicating the format.

Moreover, the information-outputting apparatus has one or morebase-band-signal input terminals each connected to an electronicapparatus and used for receiving a base-band signal generated by theelectronic apparatus, and a source-apparatus number of a base-bandsignal received through each of the base-band-signal input terminals andinformation, which indicates the format of the base-band signal in casethe base-band signal has been encoded, are added to the informationtabularized by the information-tabularizing means.

It is thereby possible for the information-outputting apparatus toreport information on base-band signals each received through abase-band-signal input terminal through the tabularized information as atable. Thus, the information-outputting apparatus is capable ofcontrolling both the connection environment of digital signals and theconnection environment of base-band signals.

In addition, the information-outputting apparatus described above alsohas apparatus-pointing means for pointing out a source apparatusgenerating a signal presently displayed on a screen in the tabularizedinformation.

The information-outputting apparatus having such apparatus-pointingmeans allows the user to recognize a source apparatus generating asignal received by the information-outputting apparatus and presentlydisplayed on a screen in the tabularized information. It is thuspossible to report an electronic apparatus serving as a sourcegenerating a signal presently displayed on a screen and other electronicapparatuses in the network with ease and with a high degree ofreliability.

The information-outputting apparatus described above further has:signal-decoding means for decoding a digital signal having apredetermined format among digital signals received by the digitalinterface unit; and decodable/undecodable judgment means for forming ajudgment as to whether or not a digital signal received by the digitalinterface unit can be decoded by the signal-decoding means, wherein theinformation-reporting means reports the fact that a digital signalreceived by the digital interface unit is undecodable to the user incase an outcome of a judgment formed by the decodable/undecodablejudgment means indicates that the digital signal is undecodable.

In the information-outputting apparatus described above, theinformation-reporting means reports the fact that a digital signalreceived by the digital interface unit is undecodable in case an outcomeof a judgment formed by the decodable/undecodable judgment meansindicates that the digital signal is undecodable.

Thus, the user of the information-outputting apparatus is capable ofknowing which electronic apparatus connected to a digital bus outputs anundecodable and, hence, normally irreproducible main digital signal, aswell as a format the digital signal has. Thus, when an undecodable and,hence, normally irreproducible main digital signal is supplied to theinformation-outputting apparatus, the user of the information-outputtingapparatus will not incorrectly interpret the abnormal playback state asa failure occurring in the information-outputting apparatus. Inaddition, the user is allowed to carry out a manual operation totransfer the transmission route of the information signal so as tosupply the main digital signal to another electronic apparatus that iscapable of decoding the signal.

The decodable/undecodable judgment means employed in theinformation-outputting apparatus provided by the present invention formsa judgment as to whether a digital signal received by the digitalinterface unit is decodable or undecodable on the basis of theinformation on a format detected by the information-detecting means.

In the information-outputting apparatus described above, information ona format detected by the information-detecting means is used by thedecodable/undecodable judgment means as a basis for forming a judgmentas to whether a digital signal received by the digital interface unit isdecodable or undecodable. Thus, the information-outputting apparatus iscapable of forming a judgment quickly as to whether a digital signalreceived by the digital interface unit is decodable or undecodablewithout the need to make an attempt to decode the signal.

In the information-outputting apparatus, the information-reporting meansreports information to the user by displaying the information on adisplay unit.

To be more specific, the information-reporting means displaysinformation on source apparatuses, information on formats and the likeon the display unit. It is thus possible to notify the user of theinformation-outputting apparatus of the information on sourceapparatuses, the information on formats and the like with a high degreeof reliability.

In the information-outputting apparatus provided by the presentinvention, the information-reporting means outputs information as asound or a voice generated by speakers.

To be more specific, the information-reporting means outputs informationon source apparatuses, information on formats and the like as a sound ora voice generated by the speakers. It is thus possible to notify theuser of the information-outputting apparatus of information on sourceapparatuses, information on formats and the like as audio informationwith a high degree of reliability.

In the information-outputting apparatus provided by the presentinvention, the information-reporting means reports information to theuser by displaying the information on a display unit, and outputsinformation as a sound or a voice generated by the speakers.

By reporting information on source apparatuses, information on formatsand the like as information displayed on a display unit, and outputtinginformation on source apparatuses, information on formats and the likeas a sound or a voice generated by the speakers, theinformation-outputting apparatus is capable of reporting the informationon source apparatuses, the information on formats and the like with ahigh degree of reliability.

The information-outputting apparatus provided by the present inventionfurther has encrypted/unencrypted judgment means for forming a judgmentas to whether or not a digital signal received by the digital interfaceunit has been encrypted, and the information-reporting means reports aresult of judgment output by the encrypted/unencrypted judgment means tothe user.

In the information-outputting apparatus described above, theencrypted/unencrypted judgment means forms a judgment as to whether ornot a digital signal received by the digital interface unit has beenencrypted, and the information-reporting means reports a result ofjudgment output by the encrypted/unencrypted judgment means. Thus, whenan encrypted main digital signal supplied to the information-outputtingapparatus cannot be decrypted and, hence, cannot be played backnormally, the user of the information-outputting apparatus will knowthat the main digital signal cannot be played back normally because thedigital signal was encrypted so that the user will not incorrectlyinterpret the abnormal playback state as a failure occurring in theinformation-outputting apparatus.

As an implementation, in the information-outputting apparatus providedby the present invention, the information-detecting means is alsocapable of detecting information indicating whether or not a digitalsignal received by the digital interface unit has been encrypted fromthe digital signal; and in this case, the encrypted/unencrypted judgmentmeans forms a judgment as to whether or not a digital signal received bythe digital interface unit has been encrypted on the basis of theinformation detected by the information-detecting means to indicatewhether or not the digital signal received by the digital interface unithas been encrypted.

As described above, in the information-outputting apparatus provided bythe present invention, the information-detecting means detectsinformation indicating whether or not a digital signal received by thedigital interface unit has been encrypted from the digital signal; andthe encrypted/unencrypted judgment means forms a judgment as to whetheror not a digital signal received by the digital interface unit has beenencrypted on the basis of the information detected by theinformation-detecting means to indicate whether or not the digitalsignal received by the digital interface unit has been encrypted.

As a result, the information-outputting apparatus is capable ofdetermining whether or not a digital signal has been encrypted with ahigh degree of reliability without the need to carry out an operationsuch as to make an attempt to decrypt the digital signal.

In addition, the information-outputting apparatus provided by thepresent invention allows an electronic apparatus connected to thenetwork to make an arbitrary access to the tabularized information.

As described above, another electronic apparatus connected to thenetwork is capable of making an arbitrary access to the tabularizedinformation in the information-outputting apparatus. Thus, anotherelectronic apparatus connected to the network is capable of making useof the tabularized information in the information-outputting apparatuswithout the need to tabularize source information IDs and information onformats into a table in the other electronic apparatus itself.

In addition, another information-outputting apparatus provided by thepresent invention is also an apparatus connected to a network comprisinga plurality of electronic apparatuses connected to each other by digitalbuses. The information-outputting apparatus comprises: one or morebase-band-signal input terminals each connected to an electronicapparatus and used for receiving a base-band signal generated by theelectronic apparatus; a digital interface unit for receiving a digitalsignal transmitted through one of the digital buses;decodable/undecodable judgment means for forming a judgment as towhether or not a digital signal received by the digital interface unitcan be decoded by the information-outputting apparatus; andinput-signal-switching means for switching a signal input so as toreceive a base-band signal from one of the base-band-signal inputterminals when an outcome of a judgment formed by thedecodable/undecodable judgment means indicates that a digital signalreceived by the digital interface unit cannot be decoded by theinformation-outputting apparatus.

As described above, in the information-outputting apparatus, theinput-signal-switching means switches the signal input so as to receivea base-band signal from one of the base-band-signal input terminals whenan outcome of a judgment formed by the decodable/undecodable judgmentmeans indicates that a main digital signal received by the digitalinterface unit cannot be decoded by the information-outputtingapparatus.

Thus, when a main digital signal received by the digital interface unitcannot be decoded by the information-outputting-apparatus, the signalinput can be switched automatically to receive a signal already decodedby another electronic apparatus connected to the same network from theother electronic apparatus without the need for the user to carry out amanual operation.

In addition, the information-outputting apparatus provided by thepresent invention further has command issuing means for issuing acommand to an electronic apparatus, which is connected to the networkand capable of decoding a digital signal, to decode the digital signaland output the decoded digital signal as a base-band signal in the caseof an outcome of a judgment formed by the decodable/undecodable judgmentmeans indicating that the same digital signal received by the digitalinterface unit cannot be decoded by the information-outputtingapparatus.

As described above, the command issuing means employed in theinformation-outputting apparatus is capable of issuing a command to anelectronic apparatus, which is connected to the network and capable ofdecoding a digital signal undecodable by the information-outputtingapparatus, to decode the digital signal and output the decoded digitalsignal as a base-band signal. Thus, it is possible to decode a desireddigital signal with a high degree of reliability and to use the decodedsignal without the need for the user to carry out a manual operation.

The digital buses employed in the information-outputting apparatusprovided by the present invention are each a bus conforming to the IEEE1394 standard.

As described above, the information-outputting apparatus employs buseseach conforming to the IEEE 1394 standard as the digital buses. Thus,digital information signals required to satisfy a real-time conditionsuch as digital video and audio signals can be transmitted at a highspeed and the copyright of the digital information signals can beprotected reliably and properly.

As described above, in accordance with the present invention, whendigital data of a content undecodable by the information-outputtingapparatus is supplied to the information-outputting apparatus,information on the content can be reported to the user or anotherapparatus external to the information-outputting apparatus. It is thuspossible to solve a problem of the user's misinterpreting a normallyirreproducible digital data due to an inability to decode the digitaldata as a failure occurring in an electronic apparatus in use.

In a network comprising a plurality of electronic apparatuses connectedto each other by digital buses, information on digital data generated byeach of the electronic apparatuses connected to the network can betabularized into a content information table. In addition, connectionstatus of the network comprising a plurality of electronic apparatusesconnected to each other by digital buses can be reported to the user andthe electronic apparatuses connected to the network.

The user can thus make use of the content information table provided bythe information-outputting apparatus as a basis for selecting an optimumsupply route of an electronic apparatus considered to be a source ofdesired digital data. It is therefore possible to improve convenienceprovided to the user in utilization of the network.

In addition, when digital data that cannot be decoded by theinformation-outputting apparatus connected to a network comprising aplurality of electronic apparatuses connected to each other by digitalbuses is supplied to the information-outputting apparatus, the digitaldata is rerouted to an electronic apparatus capable of decoding the databefore re-supplying the decoded digital data to theinformation-outputting apparatus as a base-band signal. As a result, byrerouting undecodable digital data directly supplied to theinformation-outputting apparatus to an electronic apparatus capable ofdecoding the undecodable digital data, the digital data can be used.

Moreover, by using digital buses, it is also possible to construct anetwork covering all electronic apparatuses and providing the user withconvenience and a high degree of freedom to use.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory block diagram showing connections betweenexternal apparatuses and a monitor apparatus having a digital interfaceand an analog interface (or analog I/O terminal);

FIG. 2A is an explanatory diagram showing a typical display of adecodable digital content;

FIG. 2B is an explanatory diagram showing a state of a video display ofan undecodable digital content;

FIG. 3 is an explanatory block diagram showing a monitor receiverapplying an information-outputting apparatus implemented by anembodiment of the present invention;

FIG. 4A is an explanatory block diagram used for describing anasynchronous communication method adopted in a digital interfaceconforming to the IEEE 1394 standard;

FIG. 4B is an explanatory block diagram used for describing anisochronous communication method adopted in a digital interfaceconforming to the IEEE 1394 standard;

FIG. 5 is an explanatory diagram showing the format of an isochronouspacket;

FIG. 6 is an explanatory diagram showing a typical display ofinformation on a content;

FIG. 7 is an explanatory diagram showing a typical content informationtable created in a monitor apparatus provided by the embodiment of thepresent invention;

FIG. 8 shows an explanatory flowchart representing processing to createa content information table and processing to present a contentinformation table according to a request received from an externalapparatus;

FIG. 9 is an explanatory diagram showing a typical display ofinformation on a content;

FIG. 10 is an explanatory diagram showing a typical display ofinformation according to the content information table;

FIG. 11 shows an explanatory flowchart representing processing toautomatically select a route for supplying a content in accordance withthe present invention's method for selecting a route to supply acontent;

FIG. 12 shows a continuation flowchart of the flowchart shown in FIG.11; and

FIGS. 13A and 13B are explanatory diagrams showing typical videodisplays of digital contents supplied to the monitor apparatus by way ofan automatically selected route for supplying the contents as analogsignals to be displayed thereon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description explains a preferred embodiment implementingan information-outputting apparatus, an information-reporting method andan information-signal-supply-route-selecting method provided by thepresent invention by referring to the accompanying diagrams. Thefollowing embodiment is used to exemplify a case in which aninformation-outputting apparatus provided by the present invention isapplied to a digital monitor apparatus. It should be noted that, in thefollowing description of the embodiment, an audio system employed in thedigital monitor apparatus is not explained in order to make thedescription simple.

Digital Monitor Apparatus

FIG. 3 is an explanatory block diagram showing a digital monitorapparatus 1 implemented by an embodiment of the present invention. Inthe following description, the digital monitor apparatus 1 is alsoreferred to simply as monitor apparatus 1. As will be described later,the monitor apparatus 1 implemented by the embodiment has a function toreceive a digital television broadcast and a digital interface circuitconforming to the IEEE 1394 standard as a digital interface.

This embodiment is used to exemplify a case wherein the monitorapparatus 1 is connected to a DV storage 2, an MPEG-TS (TransportStream) storage 3 and a DV camcoder 4 by digital buses each conformingto the IEEE 1394 standard and analog transmission lines to form anetwork as shown in FIG. 1. The digital buses conforming to the IEEE1394 standard are each referred to simply as a digital bus. The presentinvention is thus explained by referring also to FIG. 1 as follows.

Configuration and Operation of Digital Monitor Apparatus

As shown in FIG. 3, the monitor apparatus 1 implemented by theembodiment comprises an antenna 11, a tuner 12, a front-end unit 13, ademultiplexer 16, an MPEG decoder 17, a superposition circuit 19, adisplay circuit 20, a digital interface circuit 14 conforming to theIEEE 1394 standard, a switch circuit 15, an OSD-generating circuit 18and 3 analog input terminals S1, S2 and S3. The digital interfacecircuit 14 conforming to the IEEE 1394 standard is referred to hereafteras an IEEE 1394 I/F circuit. There is also provided a control unit 30for controlling the components of the monitor apparatus 1 implemented bythe embodiment.

In the configuration shown in FIG. 3, the control unit 30 is amicrocomputer comprising a CPU 21, a ROM 22 and a RAM 23, which areconnected to each other by a CPU bus 24. The CPU 21 executes programsstored in the ROM 22. The RAM 23 serves as a work area used by the CPU21 in carrying out various kinds of processing by execution of theprograms. The control unit 30 also includes a key operation unit 25operated by the user to enter an input.

The monitor apparatus 1 implemented by the embodiment has a receptiondisplay mode, a digital external input mode and an analog external inputmode. In the reception display mode, a digital television broadcastsignal is received, decoded with proper timing and then displayed. Inthe digital external input mode, a main digital signal received throughthe IEEE 1394 I/F circuit 14 is decoded and processed. In the analogexternal input mode, an analog signal received through the analog inputterminal S1, S2 or S3 is processed.

The modes are switched from one to another in accordance with a modeselect command input entered via the key operation unit 25 connected tothe control unit 30 of the monitor apparatus 1.

As will described later, in the monitor apparatus 1 of the embodimentoperating in the reception display mode, the control unit 30 executescontrol to drive the front-end unit 13 to demodulate a digital broadcastsignal received by the tuner 12, the demultiplexer 16 to extract data ofa program selected by the user and the MPEG decoder 17 to decode thedata or output the data to the IEEE 1394 I/F circuit 14.

In the digital external input mode, the control unit 30 executes controlto drive the demultiplexer 16 to extract data of a program selected bythe user from a data stream received by the IEEE 1394 I/F circuit 14 andthe MPEG decoder 17 to decode the data.

The reception display mode, the digital external input mode and theanalog external input mode are each described as follows.

Reception Display Mode

The description begins with an explanation of operations, which arecarried out in the monitor apparatus 1 when the reception display modeis selected. In this reception display mode, a broadcast signal D1received by the antenna 11 is supplied to the tuner 12. The tuner 12selects a desired digital broadcast signal D2 in accordance with aselect control signal received from the control unit 30, supplying theselected digital broadcast signal D2 to the front-end unit 13.

The front-end unit 13 demodulates the signal D2 received from the tuner12 and carries out error correction processing on a signal obtained as aresult of the demodulation to generate a data stream D3. The data streamD3 is multiplexed data comprising a plurality of broadcast programs andan EPG (Electronic Program Guide).

The data stream D3 generated by the front-end unit 13 is supplied to aninput terminal a of the switch circuit 15. With the reception displaymode selected by the user, the switch circuit 15 is actuated by acontrol signal D9 generated by the control unit 30.

With the reception display mode selected by the user, the switch circuit15 outputs a signal supplied to the input terminal a. Thus, the datastream D3 generated by the front-end unit 13 is supplied to thedemultiplexer 16 by way of the switch circuit 15.

The demultiplexer 16 splits data demultiplexed in the data stream D3into pieces of information such as broadcast programs and an EPG andrearranges them properly. The demultiplexer 16 extracts data of abroadcast program desired by the user in accordance with a selectcommand signal output by the control unit 30, and supplies a videostream D4 comprising packets of a video signal portion of the extractedprogram to the MPEG decoder 17.

Since the video stream D4 supplied to the MPEG decoder 17 is datacompressed by adopting the MPEG method, the MPEG decoder 17 decompressesthe video stream D4 to recover video data D5 prior to the datacompression. The MPEG decoder 17 then supplies the video data D5 to thesuperposition circuit 19. The superposition circuit 19 also receivesdisplay data called OSD (On Screen Display) data generated by theOSD-generating circuit 18.

The OSD data is superposed on video data of a picture in accordance witha control signal D10 generated by the control unit 30. Examples of theOSD data are a channel number, which is displayed when a channel iscalled by the user, a volume bar showing a volume level at volumeadjustment and a variety of messages. The superposition circuit 19superposes an OSD message on the video data D5 generated by the MPEGdecoder 17 to form a video signal D6, which is then supplied to thedisplay circuit 20.

The display circuit 20 generates a signal to be displayed on a displayunit such as a CRT from the video signal D6 received from thesuperposition circuit 19. In this way, a video of a digital broadcastprogram extracted from a digital broadcast signal received by theantenna 11 and selected by the tuner 12 is displayed on the display unitof the monitor apparatus 1.

It should be noted that, in this embodiment, the demultiplexer 16outputs a data stream supplied thereto to the IEEE 1394 I/F circuit 14as a data stream (a content) D7. The IEEE 1394 I/F circuit 14 outputsthe data stream D7 received from the demultiplexer 16 to the digital bus5 by adopting an isochronous communication method to be described laterso as to supply the data stream D7 to an electronic apparatus connectedto the network other than the monitor apparatus 1 implemented by theembodiment.

An example of the other electronic device connected to the network isthe MPEG-TS storage 3. Thus, the monitor apparatus 1 is capable ofstoring a digital broadcast signal received by the antenna 11 andselected by the tuner 12 in the MPEG-TS storage 3. It should be notedthat, as described earlier, the data stream D7 is a multiplexed signalcomprising pieces of data representing a plurality of broadcast programscompressed by adopting the MPEG method. Thus, the data stream D7 is adigital signal conforming to the so-called MPEG-TS standard.

Digital External Input Mode

Next, operations in the digital external input mode are explained. Asdescribed earlier by referring to FIG. 1, the monitor apparatus 1implemented by the embodiment is connected to a plurality of electronic(external) apparatuses by the digital buses 5, 6 and 7. When digitalsignals are received from the electronic apparatuses by way of theconnecting digital buses 5 to 7, the user of the monitor apparatus 1selects an electronic apparatus from which a digital signal should bereceived by operating the key operation unit 25.

When the user operates the key operation unit 25, the control unit 30executes control by supplying a control signal D11 to the IEEE 1394 I/Fcircuit 14 to select a transmission channel for transmitting a digitalsignal from the external apparatus selected by the user. At the sametime, the control unit 30 supplies a control signal D9 to the switchcircuit 15 to output a signal supplied to an input terminal b of theswitch circuit 15.

As described earlier, the digital buses employed in this embodiment areeach an IEEE 1394 bus, which is capable of transmitting digital data byadoption of 2 communication methods, namely, an asynchronouscommunication method and an isochronous communication method. In theisochronous communication method, transmission channels (isochronouschannels) are assigned to a plurality of electronic apparatusesconnected to the digital bus and video and audio data, which mustsatisfy real-time requirements, are transmitted, for example.

FIGS. 4A and 4B are explanatory diagrams used for explainingrespectively the asynchronous and isochronous communication methodsadopted in a digital interface conforming to the IEEE 1394 standard. Toput it in detail, the diagrams are used for explaining a procedure(sub-action) for transmitting a packet.

To be more specific, FIG. 4A is an explanatory diagram used fordescribing the asynchronous communication method. In the case of theasynchronous communication method, data of a variable amount istransmitted and a response to the data is obtained from the recipient ofthe data. As shown in FIG. 4A, in the case of the asynchronouscommunication method, a sub-action is divided into 3 main portions,namely, Arb (an arbitration sequence), a packet (data packettransmission) and Ack (an acknowledgment).

On the other hand, FIG. 4B is an explanatory diagram used for describingthe isochronous communication method. In the case of the isochronouscommunication method, data of a variable amount is transmitted to asimplified address at predetermined intervals. In the isochronouscommunication method, however, no response to the transmitted data isgiven.

As shown in FIG. 4B, in the case of the isochronous communicationmethod, there are provided a plurality of isochronous channels, namely,a first channel, a second channel, a third channel and so on. Asub-action in each isochronous channel comprises an arbitration sequence(Arb) and a packet (data packet transmission).

The IEEE 1394 I/F circuit 14 selects an isochronous channel assigned toa desired external apparatus in order to receive a data streamtransmitted by the desired external apparatus by adoption of theisochronous communication method in accordance with a control signal D11output by the control unit 30. The IEEE 1394 I/F circuit 14 thenreceives the data stream transmitted through the isochronous channel.

Selection of an isochronous channel can be based on information recordedin the header of a packet (isochronous packet) transmitted by adoptionof the isochronous communication method. FIG. 5 is an explanatorydiagram showing the format of an isochronous packet.

A channel field on the first line of the header shown in FIG. 5 is afield for recording an isochronous channel number. An SID(Source-apparatus ID) field on the third line of the header is a fieldfor recording a node ID, which is information for identifying anexternal apparatus (or a source apparatus) serving as a sourcetransmitting data as isochronous packets.

It should be noted the isochronous packet is described in detail in“IEEE 1394-1995: IEEE Standard for a High Performance Serial Bus” and“IEC61883: Consumer audio/video equipment.”

In this embodiment, the IEEE 1394 I/F circuit 14 identifies theisochronous channel number from information recorded in the SID field ofthe header of an isochronous packet received from an external apparatusspecified by the control unit 30. The IEEE 1394 I/F circuit 14 thenreceives the isochronous packet from an isochronous channel identifiedby the isochronous channel number.

In this way, the monitor apparatus 1 receives a data stream D8transmitted by adoption of the isochronous communication method from anexternal apparatus desired by the user. Then, the data stream D8received from the desired external apparatus is supplied to the inputterminal b of the switch circuit 15.

In addition, the IEEE 1394 I/F circuit 14 is capable of supplyingtypically information extracted from received data to the control unit30 as control data D12 by adoption of the asynchronous communicationmethod. Furthermore, the IEEE 1394 I/F circuit 14 is capable ofoutputting typically control data received from the control unit 30 as acontrol signal D5 to the digital bus 5 by adoption of the asynchronouscommunication method to be supplied to an external apparatus connectedto the same network.

As described above, when the monitor apparatus 1 implemented by theembodiment is set in the digital external input mode, the control signalD9 generated by the control unit 30 sets the switch circuit 15 to theinput terminal b so that the data stream D8 output by the IEEE 1394 I/Fcircuit 14 is supplied to the demultiplexer 16 by way of the switchcircuit 15.

Subsequent processing is the same as the reception display modedescribed earlier. That is to say, the demultiplexer 16 splits pieces ofdata multiplexed in the data stream D8 into programs and an EPG andrearranges the program and the EPG. The demultiplexer 16 then fetchesdata of a program desired by the user in accordance with a selectcommand signal generated by the control unit 30 and supplies a videostream D4 comprising packets of the desired program to the MPE decoder17.

The MPEG decoder 17 decompresses the video stream D4 received from thedemultiplexer 16 by adopting the MPEG method to restore the video dataD5 in a state prior to the data compression. The video data D5 issupplied to the superposition circuit 19. The superposition circuit 19superposes display data (OSD data) generated by the OSD-generatingcircuit 18 on the video data D5 received from the MPEG decoder 17 toform a video signal D6, which is then supplied to the display circuit20.

The display circuit 20 generates a signal to be displayed on a displayunit such as a CRT from the video signal D6 received from thesuperposition circuit 19 and supplies the generated signal to thedisplay unit. In this way, a video of a program extracted from a datastream transmitted by an external apparatus by way of the digital bus 5is displayed on the display unit.

By the way, provided with the demultiplexer 16 and the MPEG decoder 17,the monitor apparatus 1 implemented by the embodiment is capable ofdecoding digital data conforming to the MPEG-TS method such as a digitaltelevision broadcast and playing back the decoded data. However, themonitor apparatus 1 is not capable of decoding digital data conformingto the DV method.

That is to say, in a network built as shown in FIG. 1, it is possible todecode and play back typically digital data with an MPEG-TS formattransmitted through a digital bus from the MPEG-TS storage 3. However,it is impossible to decode and play back digital data with a DV formattransmitted from the DV storage 2 or the DV camcoder 4 by way of adigital bus.

Thus, the monitor apparatus 1 implemented by the embodiment is notcapable of displaying a video even if digital data is received from theDV storage 2 or the DV camcoder 4 since the digital data cannot bedecoded. It is quite within the bounds of possibility that the user notfamiliar with these kinds of equipment incorrectly thinks that a failureoccurs in the DV storage 2, the DV camcoder 4 or the monitor apparatus 1in case no video is displayed.

In order to solve the problem described above, when digital data thatcannot be decoded by the monitor apparatus 1 implemented by theembodiment is supplied to the monitor apparatus 1, the monitor apparatus1 notifies the user of the isochronous channel number, the sourceinformation ID and the information on the format of the digital data bydisplaying the isochronous channel number, the source information ID andthe information on the format on the display unit employed in themonitor apparatus 1.

The information on the format includes information indicating one of avariety of encoding methods including data compressing and encodingmethods such as the DV method, the MPEG method and the JPEG method. Theinformation on the format also includes information indicatingtransmission method parameters such as the number of bits per worddetermined for transmitting digital data, a header size, header itemsand a packet size. Thus, the information on a format is information thatcan be used for determining a cause of an inability to decode digitaldata due to a difference in encoding method or a difference intransmission method.

In the monitor apparatus 1 implemented by the embodiment, as describedearlier, information on a format includes information indicating acompressing and encoding method adopted for digital data supplied to themonitor apparatus 1. The information indicating a compressing andencoding method in this embodiment is referred to hereafter as formatinformation.

That is to say, in the case of an IEEE 1394 bus, as described earlier byreferring to FIG. 5, the header of an isochronous packet includes anisochronous channel number in the channel field, a source apparatus IDin the SID field and format information in the FMT field indicating acompressing and encoding method adopted for compressing and encodingdigital data transmitted by using the isochronous packet.

The IEEE 1394 I/F circuit 14 extracts a transmission channel number ofthe channel field, a source apparatus ID of the SID field and formatinformation of the FMT field from the header of a selectively receivedisochronous packet, supplying the transmission channel number, thesource apparatus ID and the format information to the control unit 30.The control unit 30 determines whether digital data to be processed hasbeen compressed and encoded by adopting a compressing and encodingmethod that allows the monitor apparatus 1 to decompress and decode thedigital data. The formation of the judgment is based on the formatinformation extracted from the FMT field of the header of theisochronous packet of the digital data received by the monitor apparatus1. If the digital data cannot be decompressed and decoded, that is, ifthe digital data has been encoded by adoption of the DV method in thecase of this embodiment, the control unit 30 passes on the transmissionchannel number of the channel field, the source apparatus ID of the SIDfield and the format information of the FMT field received from the IEEE1394 I/F circuit 14 to the OSD-generating unit 18.

The OSD-generating unit 18 generates OSD information showing thetransmission channel number, the source apparatus ID and the formatinformation from the transmission channel number of the channel field,the source apparatus ID of the SID field and the format information ofthe FMT field received from the control unit 30, supplying the OSDinformation to the superposition circuit 19.

Thus, when the user of the monitor apparatus 1 implemented by theembodiment prefers to receive digital data from the DV storage 2 or theDV camcoder 4 by way of one of the digital buses, the screen G of thedisplay apparatus 1 displays a transmission channel or an isochronouschannel number extracted from the channel field, a source apparatus IDextracted from the SID field and format information extracted from theFMT field as shown in FIG. 6.

FIG. 6 is an explanatory diagram showing a typical display ofinformation on a packet, which appears on the display screen G of themonitor apparatus 1 implemented by the embodiment when the user of themonitor apparatus 1 prefers to receive digital data from, for example,the DV storage 2 in the network.

As described above, when the monitor apparatus 1 implemented by theembodiment receives digital data, which cannot be decoded by the monitorapparatus 1, the monitor apparatus 1 notifies the user of the monitorapparatus 1 of which isochronous channel is used for receiving thedigital data, which external apparatus is supplying the digital data andwhich comprising and encoding method was adopted by the externalapparatus to generate the digital data.

Thus, the user of the monitor apparatus 1 is capable of knowing thatdigital data received from its own selected external apparatus isdigital data compressed and encoded by adopting a compressing andencoding method that makes it impossible for the monitor apparatus 1 todecompress and decode the digital data.

It should be noted that a user not familiar with the monitor apparatus 1may not be capable of immediately understanding the reason why no videodisplay appears on the screen by merely being informed of a transmissionchannel, a source apparatus ID and format information. In order to solvethis problem, the monitor apparatus 1 may display a typical message of“Since digital data received from a DV storage identified by a sourceapparatus ID of 2 is data having a DV format, the digital data cannot bedecoded by the monitor apparatus.” or “Since digital data received froma DV storage identified by a source apparatus ID of 1 is data having anincompatible format, the digital data cannot be displayed by the monitorapparatus.”

Such a message is stored in the ROM 22 employed in the control unit 30in advance and, if format information received from the IEEE 1394 I/Fcircuit 14 indicates that a DV signal is received, the control unit 30retrieves the message from the ROM 22 and supplies the message to theOSD-generating unit 18.

It should be noted that, in the description of the embodiment, an audiosystem employed in the monitor apparatus 1 implemented by the embodimentis not explained in order to make the description simple as describedabove. Thus, in addition to a displayed message, an audio message canalso be output from the speakers SP1 and SP2 employed in the monitorapparatus 1. In this case, at a stage before the speakers SP1 and SP2,there is provided a message-generating circuit for generating an audiomessage according to control executed by the control unit 30 andsupplying the message to the speakers SP1 and SP2. It is needless to saythat an audio message can be output by adopting another method.

As described above, when digital data, which cannot be decoded and,hence, displayed, is supplied to the monitor apparatus 1, the monitorapparatus 1 informs the user of an isochronous channel number, a sourceapparatus ID and format information through typically a display,preventing the user from incorrectly misinterpreting the undisplayeddigital data as a failure occurring in an apparatus.

In addition, reporting of an isochronous channel number, a sourceapparatus ID and format information typically as a display as describedabove allows a countermeasure to be taken to solve the problem bymanually changing the transmission route of digital data, for example,by having the digital data rerouted to an external apparatus capable ofdecoding the digital data before supplying back the data to the monitorapparatus 1.

Moreover, the monitor apparatus 1 implemented by the embodiment usesformat information extracted from the FMT field of the header of anisochronous packet as a basis for determining whether or not digitaldata received by the IEEE 1394 I/F circuit 14 is digital data having aformat allowing the monitor apparatus 1 to decode the data. It should benoted, however, that the scope of the present invention is not limitedto this scheme.

For example, digital data received by the IEEE 1394 I/F circuit 14 isdecoded, and the decoded data is used as a basis for determining whetheror not the digital data is digital data having a format allowing themonitor apparatus 1 to decode the data. That is to say, a variety ofmethods may be adopted for determining whether or not digital datareceived by the IEEE 1394 I/F circuit 14 is digital data having a formatallowing the monitor apparatus 1 to decode the data.

By using format information extracted from the FMT field of the headerof an isochronous packet as a basis for determining whether or notdigital data received by the IEEE 1394 I/F circuit 14 is digital datahaving a format allowing the monitor apparatus 1 to decode the data,nevertheless, it becomes unnecessary to decode the digital data. Thus,it is possible to determine whether or not digital data received by theIEEE 1394 I/F circuit 14 is digital data having a format allowing themonitor apparatus 1 to decode the data in a short period of time.

Analog External Input Mode

Next, operations carried out in the analog external input mode areexplained. As shown in FIG. 1, the DV storage 2, the MPEG-TS storage 3and the DV camcoder 4 are connected to the monitor apparatus 1implemented by the embodiment through the analog signal cables 8, 9 and10 respectively. The user of the monitor apparatus 1 is allowed tooperate the key operation unit 25 to select one of the DV storage 2, theMPEG-TS storage 3 and the DV camcoder 4 connected to the monitorapparatus 1 through the analog signal cables 8, 9 and 10 respectively asa source apparatus for generating an analog signal to be supplied to themonitor apparatus 1.

In this embodiment, the DV storage 2, the MPEG-TS storage 3 and the DVcamcoder 4 are connected to the analog input terminals S1, S2 and S3 ofthe monitor apparatus 1 respectively. Analog signals received at theanalog input terminals S1, S2 and S3 are supplied to the superpositioncircuit 19.

In this embodiment, the superposition circuit 19 is capable of selectingone of the analog signals received at the analog input terminals S1, S2and S3 as a signal to be processed in accordance with control executedby the control unit 30. Then, the superposition circuit 19 superposesOSD information received from the OSD-generating circuit 18 on theselected analog signal, outputting the OSD information and the analogsignal to the display circuit 20 as a video signal D6.

The display circuit 20 generates a signal to be displayed on a displayunit such as a CRT from the video signal D6 received from thesuperposition circuit 19 and supplies the generated signal to thedisplay unit. In this way, a video conveyed by an analog video signalreceived from an external apparatus by way of one of the analog signalcables 8, 9 and 10 is displayed on the display unit.

As described above, the monitor apparatus 1 implemented by theembodiment has 3 modes, namely, the reception display mode, the digitalexternal input mode and the analog external input mode. Also asdescribed above, when digital data that cannot be decoded by the monitorapparatus 1 is received in the digital external input mode, theisochronous channel number, the source apparatus ID and the formatinformation are reported. Thus, when no video display appears on thescreen because of reception of undecodable digital data, the user of themonitor apparatus 1 does not incorrectly interpret the screen with novideo display as a failure occurring in an apparatus.

As described above, in this embodiment, an isochronous channel number, asource apparatus ID and format information are reported only whendigital data that cannot be decoded by the monitor apparatus 1 isreceived. It should be noted, however, that the scope of the presentinvention is not limited to this scheme.

In the digital external input mode, for example, an isochronous channelnumber, a source apparatus ID and format information are reportedwithout regard to whether or not digital data received from an externalapparatus can be decoded by the apparatus and the reporting is endedafter a predetermined period of time lapses or when the user enters anacknowledgement in response to the report.

In the above description, the superposition circuit 19 employed in themonitor apparatus 1 shown in FIG. 3 is explained as a circuit forsuperposing OSD information on a video signal. It should be noted,however, that the superposition circuit 19 is also capable of forming apicture to be displayed on a screen by synthesizing typically 4different video signals, namely, a video signal generated by the MPEGdecoder 17 and video signals input from the 3 analog input terminals S1,S2 and S3.

When forming a picture to be displayed on a screen by synthesizing aplurality of different video signals one of which cannot be displayed asdescribed above, the monitor apparatus 1 displays an isochronous channelnumber, a source apparatus ID and format information in an area on thescreen for a video portion of the undecodable signal or over the entirescreen.

Creation of Content Information Table

By the way, as described earlier by referring to FIG. 6, when themonitor apparatus 1 operating in the digital external input modereceives digital data, which cannot be decoded thereby, the monitorapparatus 1 reports an isochronous channel number, a source apparatus IDand format information to the user so that the user does not incorrectlyinterpret the screen with no video display as a failure occurring in anapparatus.

As described above, however, a concrete countermeasure can be taken tosolve the no-display problem by manually changing the transmission routeof digital data, for example, by having the digital data rerouted to anexternal apparatus capable of decoding the digital data before supplyingthe data back to the monitor apparatus 1. In this case, nevertheless,the transmission route of the digital data cannot be changed quicklyunless the user knows external apparatuses and types of digital data theexternal apparatuses are capable of decoding.

When an attempt is made to dub digital data generated by the DV storage2 in a network with a plurality of external apparatuses connectedthereto as shown in FIG. 1, for example, it is quite within the boundsof possibility that the user does not know which external apparatus iscapable of dubbing the digital data.

In order to solve this problem, in this embodiment, information oncontents or signals supplied to the monitor apparatus 1 is tabularizedinto a content information table, which is stored in a memory to bereported to the user through the monitor apparatus 1 or another externalapparatus in order to offer more convenience to the user.

FIG. 7 is an explanatory diagram showing a typical content informationtable created in the monitor apparatus 1 by tabularizing information oncontents or signals supplied to the monitor apparatus 1. A transmissionchannel number column, a transmission source ID column and a formatcolumn correspond to respectively the isochronous channel number field,the source apparatus ID (SID) field and the format information (FMT)field in the header of an isochronous packet described earlier byreferring to FIG. 5.

Information on an encryption column indicates whether or not digitaldata has been encrypted. This information can also obtained from theheader of an isochronous packet shown in FIG. 5. To be more specific,information in an EMI field in the header of an isochronous packet shownin FIG. 5 is a control code for encryption of the content and can thusbe used to indicate whether or not the digital data has been encrypted.To put it in detail, the information in the EMI field indicates whetheror not the digital data or the digital content transmitted by using thispacket has been encrypted.

The IEEE 1394 I/F circuit 14 employed in the monitor apparatus 1implemented by the embodiment changes the isochronous channel from oneto another to scan for an isochronous packet that is receivable. Then,the IEEE 1394 I/F circuit 14 extracts necessary data from the header ofa received isochronous packet. Finally, the extracted data istabularized to form a content information table like the one shown inFIG. 7.

It should be noted that the control unit 30 employed in the monitorapparatus 1 recognizes which mode the monitor apparatus 1 is presentlyoperating in and which external apparatus is currently supplyinginformation to the monitor apparatus 1. A specifier denoted by a circlemark is appended on an active row representing an external apparatuscurrently supplying a signal conveying a content currently displayed asa picture on the monitor apparatus 1. The circle mark distinguishes theactive row from the others. In the content information table shown inthe figure, the active first row indicates that an external apparatuswith a transmission source ID of 2 is currently supplying an unencrypteddigital signal of the DV format.

In addition, the monitor apparatus 1 implemented by the embodiment isprovided with the 3 analog input terminals S1, S2 and S3 each used forreceiving an analog signal. The fact that an analog transmission line isconnected to any of the 3 analog input terminals S1, S2 and S3 can besensed by mechanical means or by detection of the impedance of theanalog transmission line, the voltage level of the signal or the like.

Unlike a digital signal received by the IEEE 1394 I/F circuit 14 asdescribed earlier, however, it is impossible to automatically detectinformation indicating which analog input terminal is currentlyreceiving an analog signal or which external apparatus is presentlysupplying an analog signal and what analog signal is currently beingsupplied. In order to solve this problem, in this embodiment, the userof the monitor apparatus 1 enters information on analog signals suppliedto the analog input terminals S1, S2 and S3 via the key operation unit25.

At that time, the content information table shown in FIG. 7 is displayedon the screen G of the display unit employed in the monitor apparatus 1.On the lower part of the content information table, analog signal rowseach representing an analog connection are created like digital signalrows each representing a digital connection. Much like the digitalsignal rows, each of the analog signal rows of the content informationtable shows information on the analog connection, which is entered bythe user typically via the key operation unit 25.

In the case of the network wherein the DV storage 2, the MPEG-TS storage3 and the DV camcoder 4 are connected to the digital monitor apparatus 1as shown in FIG. 1, for example, information on digital data supplied tothe IEEE 1394 I/F circuit 14, that is, information described on digitalsignal rows of the content information table shown in FIG. 7, can beautomatically detected by scanning as described above.

Then, while looking at the information on digital data obtained byautomatic detection and described on the digital signal rows of thecontent information table, the user sets analog connections eachcorresponding to one of the digital connections. That is to say, in thecase of the network shown in FIG. 1, the analog outputs of the DVstorage 2, the MPEG-TS storage 3 and the DV camcoder 4 are connected tothe analog input terminals S1, S2 and S3 of the monitor apparatus 1respectively.

The analog connections each corresponding to one of the digitalconnections are set by copying pieces of information described on thedigital signal rows of the content information table to the analogsignal rows as they are as shown in FIG. 7. In this way, pieces ofinformation on analog signals supplied to the monitor apparatus 1 can bedescribed on the analog signal rows of the content information table bymerely copying information on digital data supplied to the IEEE 1394 I/Fcircuit 14 employed in the monitor apparatus 1, that is, informationdescribed on digital signal rows, which can be automatically detected byscanning as described above.

Information on an analog signal in the content information table shownin FIG. 7 includes a transmission channel number, a transmission sourceID, a format and information on encryption. The transmission channelnumber is an analog transmission number assigned to the analog inputterminal S1, S2 or S3 receiving this analog signal. The transmissionsource ID is a source apparatus ID (SID) assigned to a digitallyconnected external apparatus generating this analog signal. The formatis the format information extracted from the FMT field of digital datarepresenting a content output as this analog signal. The information onencryption is information in the EMI field of digital data representinga content output as this analog signal. As described earlier, theinformation in the EMI field indicates whether or not the digital datahas been encrypted.

As described above, each analog connection can be associated with adigital connection, and the monitor apparatus 1 is capable ofcontrolling analog and digital connections as a content informationtable like the one shown in FIG. 7.

Much like the information on the digital signals, the information on theanalog signals can also be added automatically to the contentinformation table shown in FIG. 7 if the information on the analogsignals can be transmitted from the external apparatuses connected tothe input terminals S1, S2 and S3 of the monitor apparatus 1 to themonitor apparatus 1 through the analog transmission lines connected tothe input terminals S1, S2 and S3, by radio communication or throughother transmission lines.

By utilizing the functions of the IEEE 1394 bus, the monitor apparatus 1implemented by the embodiment is capable of supplying part or all of thecontent information table of FIG. 7 created in the monitor apparatus 1to an external apparatus connected to the network at a request made bythe external apparatus.

With such a capability of the monitor apparatus 1, each of the externalapparatuses connected to the network shown in FIG. 1 is capable ofknowing which of the external apparatuses is currently supplying data tothe monitor apparatus 1 and what type of data is presently beingsupplied thereto. As described above, the monitor apparatus 1 itself iscapable of determining whether or not the signal representing the datacan be decoded by the monitor apparatus 1. In addition, the user of thenetwork is capable of knowing connection status of the network from thecontent information table. For example, the user is capable of knowingwhich of the external apparatuses is capable of processing a signal,which is supplied by another external apparatus but cannot be processedby the monitor apparatus 1.

The following description explains pieces of processing carried out bythe monitor apparatus 1 implemented by the embodiment to create acontent information table and to respond to an inquiry about the contentinformation table by referring to a flowchart shown in FIG. 8.

When the control unit 30 employed in the monitor apparatus 1 of theembodiment enters a state of being capable of carrying out operations atthe time the power supply of the monitor apparatus 1 is turned on, theprocessing represented by the flowchart shown in FIG. 8 is carried out.As shown in the figure, the flowchart begins with a step S101 at whichthe control unit 30 employed in the monitor apparatus 1 sets a variablen at 0. The variable n is the number of already scanned isochronouschannels or already scanned transmission channels through which signalsare received through the IEEE 1394 I/F circuit 14. Then, at the nextstep S102, the control unit 30 sets isochronous channel n in the IEEE1394 I/F circuit 14 and connects the monitor apparatus 1 to isochronouschannel n.

It is the CPU 21 that sets an isochronous channel in the IEEE 1394 I/Fcircuit 14 through the CPU bus 24. When an isochronous channel is set,the IEEE 1394 I/F circuit 14 selects isochronous data of the setisochronous channel received through an IEEE 1394 bus and extractsisochronous packets, that is, pieces of data packetized for theisochronous channel.

For the reason described above, the IEEE 1394 I/F circuit 14 employed inthe embodiment is provided with a plurality of possible isochronouschannels settings each used for receiving content information incomingthrough an IEEE 1394 bus by adoption of a polling method. That is tosay, by sequentially changing the isochronous channel setting from oneto another, the IEEE 1394 I/F circuit 14 is capable of selecting datareceived through a set isochronous channel and extracting isochronouspackets, that is, pieces of data packetized for the isochronous channel,from the selected channel.

Then, at the next step S103, the IEEE 1394 I/F circuit 14 extractsinformation indicating whether or not the selected data has beenencrypted, a source apparatus ID and format information respectivelyfrom the EMI, SID and FMT fields of the header of an extractedisochronous packet, which was explained earlier by referring to FIG. 5,supplying the information on encryption, the source apparatus ID and theformat information to the control unit 30.

Subsequently, at the next step S104, the control unit 30 employed in theembodiment creates a content information table in the RAM 23. To put itin detail, the control unit 30 receives the information on dataencryption, the source apparatus ID and the format informationrespectively extracted from the EMI, SID and FMT fields by the IEEE 1394I/F circuit 14, putting the information on data encryption, the sourceapparatus ID and the format information in an entry of the contentinformation table created in the RAM 23 along with an isochronouschannel number or a transmission channel number associated with theentry. The isochronous channel number or the transmission channel numberis determined by the variable n.

Then, at the next step S105, the control unit 30 increments the variablen by 1 in order to go to a next isochronous channel in achannel-scanning operation. Subsequently, at the next step S106, thevariable n is examined to form a judgment as to whether the variable nhas not exceeded a maximum value of the number of isochronous channels,which is 63 as prescribed in IEEE 1394-1995 specifications.

If the outcome of the judgment formed at the step S106 indicates thatthe variable n has not exceeded the maximum value of the number ofisochronous channels, the flow of the processing goes on to a step S107at which the active row of the content information table is made valid.The active row includes pieces of information for a content superposedin the superposition circuit 19 and currently being watched and listenedto. The content superposed in the superposition circuit 19 and currentlybeing watched and listened to is determined by the superposition circuit19 in accordance with control executed by the control unit 30 and inaccordance with a command entered by the user.

Then, at the next step S108, the control unit 30 forms a judgment as towhether or not an external apparatus connected to the network has madean inquiry about the content information table through the IEEE 1394 busand the IEEE 1394 I/F circuit 14. The control unit 30 forms the judgmentas to whether or not an external apparatus connected to the network hasmade an inquiry about the content information table on the basis of anisochronous communication from the external apparatus to the monitorapparatus 1 through a digital bus between the external apparatus to themonitor apparatus 1.

If the outcome of the judgment formed at the step S108 indicates that anexternal apparatus connected to the network has made an inquiry aboutthe content information table, the flow of the processing goes on to astep S109 at which some or all of information in the content informationtable created in the RAM 23 is transmitted to the external apparatusmaking the inquiry though the IEEE 1394 I/F circuit 14 and the IEEE 1394bus. Then, the flow of the processing goes back to the step S101 torepeat the processing from this step.

If the outcome of the judgment formed at the step S108 indicates that noexternal apparatus connected to the network has made an inquiry aboutthe content information table, on the other hand, the flow of theprocessing goes back to the step S101 to repeat the pieces ofprocessing.

A judgment as to whether some or all of information in the contentinformation table is to be transmitted to the external apparatus makingthe inquiry is formed in accordance with the inquiry. If the outcome ofthe judgment indicates that only some of information in the contentinformation table is to be transmitted, some of the information may beonly information on the external apparatus making the inquiry or onlyinformation on external apparatuses other than the external apparatusmaking the inquiry.

As an alternative, all of the information in the content informationtable is always transmitted to the external apparatus making the inquiryand, at the recipient external apparatus, the information is furtherprocessed to produce a final output.

As described above, content information transmitted by adoption of anisochronous communication method through IEEE 1394 buses is scanned bysequentially changing the isochronous channel from one to another tomonitor digital data handled through the isochronous channels andacquire information on the digital data without the need for the user tocarry out a manual operation.

On the other hand, information on a content supplied as an analog signalto the monitor apparatus 1 by an external apparatus connected to themonitor apparatus 1 by an analog signal cable is acquired and setmanually by the user. In this way, a content information table includingboth information on analog contents and information on digital contentsis created and stored in the monitor apparatus 1 to be presented to theuser of the monitor apparatus 1 or an external apparatus connected tothe network.

In addition, by displaying the content information table created in theapparatus on the screen of the display unit employed in the monitorapparatus 1 as shown in FIG. 7, it is possible to inform the user of themonitor apparatus 1 of connection status of the network to which themonitor apparatus 1 is connected.

It is also possible to draw connection status of the network connectingthe monitor apparatus 1 to other external apparatuses based on thecontent information table on the screen as shown in FIG. 9. In order todisplay the entire content information table shown in FIG. 7 or to drawthe connection status of the network shown in FIG. 9 as described above,the control unit 30 supplies display information to the OSD-generatingcircuit 18.

In the connection status of the network drawn on the screen, atransmission line currently being used is typically represented by athick line as shown in FIG. 9 so as to enable the user to distinguishsuch a line from others. As an alternative, the color or the brightnessof such a transmission line is made different from those of the others.As another alternative, such a transmission line is displayed in ablinking state. In this way, the user is capable of recognizing whichexternal apparatus is currently supplying a signal to the monitorapparatus 1 at a glance.

When an incorrect selection is made so that undecodable digital data isinadvertently received as indicated by a displayed screen shown in FIG.6 in a process to create a content information table, information on thedigital data can be displayed on the display screen G of the displayunit employed in the monitor apparatus 1. It is needless to say that,even if decodable digital data is selected, information on the digitaldata can also be displayed on the display screen G of the display unitemployed in the monitor apparatus 1, being superposed on a video displayof the digital data.

As described above, in this embodiment, if it is obvious that a relationbetween external apparatuses connected to the monitor apparatus 1 byanalog signal cables and the analog terminals S1, S2 and S3 of themonitor apparatus 1 is set univocally by the user, a video display of asupplied analog content can be displayed, being superposed on aninformative message, which is displayed when the analog content issupplied inadvertently as digital data as shown in FIG. 10.

As described above, in the embodiment shown in FIG. 1, the DV storage 2,the MPEG-TS storage 3 and the DV camcoder 4 are connected to the monitorapparatus 1 by analog and digital signal cables. It should be noted,however, that the scope of the present invention is not limited to anetwork wherein each of the external apparatuses is connected to themonitor apparatus 1 by digital and analog signal cables. The presentinvention can also be applied to a case in which there are an externalapparatus connected to the monitor apparatus 1 only by an analog signalcable as well as an external apparatus connected to the monitorapparatus 1 only by a digital signal cable.

In addition, in the embodiment, a circle mark on the active row of thecontent information table shown in FIG. 7 is used as a specifier forindicating which content information is now being selected in themonitor apparatus 1. Thus, network connection status can be displayedwith a transmission in use emphasized as shown in FIG. 9 describedearlier. In addition, the user of the monitor apparatus 1 and anexternal apparatus can be informed of which external apparatus ispresently supplying a signal to the monitor apparatus 1.

In the display of the content information table shown in FIG. 7 on thescreen of the display unit employed in the monitor apparatus 1,information on a content presently being used, that is, a sourceapparatus ID showing a source supplying a content being used in thecurrent picture display and format information, may be displayedinversely or displayed in a blinking state to distinguish thisinformation from information on contents, which are supplied fromanother external apparatus and not being currently used in the monitorapparatus 1.

In addition, the content information table created in the monitorapparatus 1 like the one shown in FIG. 7 can be effectively used inprocesses such as dubbing of digital data from an external apparatusconnected to the network to another as follows.

Assuming for example that the DV camcoder 4 is supplying an analogcontent to the monitor apparatus 1 through the analog signal cable 10 inthe network shown in FIG. 1, the user watching a video display of theanalog content appearing on the screen of the display unit employed inthe monitor apparatus 1 may want to copy the content currently beingplayed back to another electronic apparatus.

In such a case, by referring to the content information table displayedon the screen of the display unit employed in the monitor apparatus 1 orthe network connection status drawn on the screen, the user is capableof knowing the source apparatus, the compressing and encoding method andthe information on encryption of the content currently being displayedon the screen. Thus, the user is capable of forming a judgment as towhether the DV storage 2 or the MPEG-TS storage 3 is capable ofdecrypting the signal correctly and, hence, properly copying thecontent.

In addition, in the case of the network shown in FIG. 1, assuming thatthe user determines the DV storage 2 to be the proper external apparatuscapable of copying digital data generated by the DV camcoder 4, it ispossible to issue a request for digital dubbing from the DV storage 2 tothe DV camcoder 4. Such a request is initiated by issuing a command tothe DV storage 2 to receive digital data from the DV camcoder 4 andrecord the data. Receiving such a command, the DV storage 2 outputs arequest to the DV camcoder 4 to provide the digital data to the DVstorage 2.

At the request issued by the DV storage 2 to the DV camcoder 4 toprovide digital data, the DV camcoder 4 supplies the digital data to theDV storage 2, which then records the data. That is to say, the contentsupplied by the DV camcoder 4 to the monitor apparatus 1 as an analogsignal can be stored in a recording medium employed in the DV storage 2as digital data.

Automatic Selection of a Content Supply Route

As described before, the monitor apparatus 1 implemented by theembodiment displays the transmission channel number, the sourceapparatus ID and the format information of a content supplied to themonitor apparatus 1. As an alternative, the monitor apparatus 1 maydisplay connection status of the network connecting the apparatus as acontent information table, or draws the status on the screen.

Even if these pieces of information are displayed, nevertheless, it isquite within the bounds of possibility that a user not familiar with themonitor apparatus 1 or the external apparatuses connected to the monitorapparatus 1 by the network is not capable of quickly thinking of an ideaas to how to operate the monitor apparatus 1 in order to display a videoof a content the user wants to watch and listen to and, hence, notcapable of dealing with the situation.

In order to solve the problem described above, the monitor apparatus 1implemented by the embodiment is provided with an automatic selectfunction for automatically selecting a content supply route. By settingthe monitor apparatus 1 to execute this function, a route for supplyinga digital content is automatically selected so that a video display ofthe content can be output even if the monitor apparatus 1 is not capableof decoding the digital data of the content. As a result, the monitorapparatus 1 is capable of outputting the video display of a digitalcontent even if the monitor apparatus 1 is not capable of decoding thedigital data of the content.

The automatic select function for automatically selecting a contentsupply route is set by storing information entered by operating the keyoperation unit 25 in the RAM 23 employed in the control unit 30. It isthus necessary to employ a non-volatile memory as the RAM 23 so thatsetting information stored in the RAM 23 remains stored even if thepower supply of the monitor apparatus 1 is turned off. It is needless tosay that, as an alternative, a non-volatile memory used dedicatedly forstoring various kinds of setting information can also be providedseparately from the RAM 23.

If the automatic select function for automatically selecting adigital-content supply route stored in the RAM 23 is in an ON state,when the power supply of the monitor apparatus 1 implemented by theembodiment is turned on, the control unit 30 put in the digital externalinput mode described earlier carries out automatic select processing forautomatically selecting a digital-content supply route in accordancewith a flowchart shown in FIGS. 11 and 12.

As described before, with the digital external input mode set, the IEEE1394 I/F circuit 14 controlled by the control unit 30 extractsisochronous packets of an isochronous channel assigned to an externalapparatus specified by the user at a step S201. The IEEE 1394 I/Fcircuit 14 then obtains an isochronous channel number of the channelfield and format information of the FMT field from the header of one ofthe isochronous packets, supplying the isochronous channel number andthe format information to the control unit 30.

At the next step S202, the control unit 30 examines the formatinformation received from the IEEE 1394 I/F circuit 14 to form ajudgment as to whether or not digital data received through theisochronous channel has been compressed and encoded by adoption of amethod that allows the monitor apparatus 1 to decode the digital data,that is, whether or not the digital data has a format that allows themonitor apparatus 1 to decode the digital data.

If the outcome of the judgment formed at the step S202 indicates thatthe digital data received through the isochronous channel has beencompressed and encoded by adoption of a method, which allows the monitorapparatus 1 to decode the digital data, the flow of the processing goeson to a step S212 at which a digital content obtained as a result of adecoding process is displayed on the screen of the display unit employedin the apparatus in accordance with the processing carried out in thedigital external input mode as described earlier. Then, the processingrepresented by the flowchart shown in FIGS. 11 and 12 is ended.

If the outcome of the judgment formed at the step S202 indicates thatthe digital data received through the isochronous channel has beencompressed and encoded by adoption of a method, which does not allow themonitor apparatus 1 to decode the digital data, on the other hand, theflow of the processing goes on to a step S203 at which the user isinformed that the digital data received through the isochronous channelcannot be decoded and requested to enter a response indicating a desireto terminate the operation to play back the content or a responseindicating a desire to find an external apparatus capable of decodingthe digital data. That is to say, the flow of the processing goes on tothe step S203 to form a judgment as to whether or not to find anexternal apparatus capable of decoding the digital data.

If the outcome of the judgment formed at the step S203 indicates thatthe user wants to terminate the operation to play back the content, theprocessing represented by the flowchart shown in FIGS. 11 and 12 ismerely ended. If the outcome of the judgment formed at the step S203indicates that the user wants to find an external apparatus capable ofdecoding the digital data, on the other hand, the flow of the processinggoes on to a step S204 at which the control unit 30 sets a variable m at0. Then, at the next step S205, the IEEE 1394 I/F circuit 14 transmitsan inquiry to an external apparatus with a node IDm through a digitalbus by adoption of the isochronous communication method. The inquirytransmitted to the external apparatus is an inquiry about whether or notthe external apparatus is capable of decoding the digital data, whichwas compressed and encoded by using a method indicated by the formatinformation extracted at the step S201.

Then, at the next step S206, the control unit 30 forms a judgment as towhether or not a reply transmitted by the external apparatus with thenode IDm through the digital bus and the IEEE 1394 I/F circuit 14 inresponse to the inquiry made at the step S205 indicates that theexternal apparatus is capable of decoding the digital data, which wascompressed and encoded by using a method indicated by the formatinformation.

If the outcome of the judgment formed at the step S206 suggests that thereply transmitted by the external apparatus with the node IDm indicatesthat the external apparatus is not capable of decoding the digital data,which was compressed and encoded by using a method indicated by theformat information, the flow of the processing goes on to a step S207 atwhich the control unit 30 increments the variable m by 1. Then, the flowof the processing goes on to a next step S208 to form a judgment as towhether or not the variable m has exceeded a maximum value of the nodeID.

If the outcome of the judgment formed at the step S208 suggests that thevariable m has exceeded the maximum value of the node ID, the flow ofthe processing goes on to a step S211 of the continuation flowchartshown in FIG. 12. At the step S211, the control unit 30 displays amessage on the screen of the display unit employed in the monitorapparatus 1 to notify the user that no external apparatus capable ofdecoding the digital data, which was compressed and encoded by using amethod indicated by the format information, is connected to the networkof the monitor apparatus 1. Then, the processing represented by theflowchart shown in FIGS. 11 and 12 is ended. If the outcome of thejudgment formed at the step S208 suggests that the variable m has notexceeded the maximum value of the node ID, on the other hand, the flowof the processing goes back to the step S205 to repeat the processingfrom this step.

If the outcome of the judgment formed at the step S206 suggests that thereply transmitted by the external apparatus with the node IDm indicatesthat the external apparatus is capable of decoding the digital data,which was compressed and encoded by using a method indicated by theformat information, on the other hand, the flow of the processing goeson to a step S209 of the continuation flowchart shown in FIG. 12. At thestep S209, the control unit 30 requests the IEEE 1394 I/F circuit 14 tooutput a command to the external apparatus indicated by the node IDmthrough a digital bus to request that the external apparatus receiveisochronous packets of an isochronous channel indicated by theisochronous channel number acquired at the step S201, decode the packetsand transmit results of decoding as an analog signal to the monitorapparatus 1.

In addition, in this embodiment, each analog connection is associatedwith a digital connection, and a content information table explainedbefore by referring to FIG. 7 is created in advance as describedearlier. Thus, by examining the formats and the node ID (or node IDm) ofan external apparatus capable of decoding digital data in the contentinformation table, the control unit 30 is capable of finding an externalapparatus capable of decoding the digital data compressed and encoded bythe method indicated by the format information acquired at the step S201and capable outputting results of decoding as an analog signal to themonitor apparatus 1. The control unit 30 is thereby also capable ofidentifying which analog input terminal of the monitor apparatus 1 isconnected to the external apparatus.

Then, at the next step S210, the control unit 30 controls thesuperposition circuit 19 to output the analog signal received from theexternal apparatus through the analog input terminal as a result ofdecoding the digital data, which was compressed and encoded by themethod indicated by the format information acquired at the step S201.Finally, the processing represented by the flowchart shown in FIGS. 11and 12 is ended.

As described above, when the monitor apparatus 1 receives digital data,which was compressed and encoded by a method making it impossible forthe monitor apparatus 1 to decompress and decode the digital data,through the digital bus 5 and the IEEE 1394 I/F circuit 14, the monitorapparatus 1 reroutes the digital data to an external apparatus capableof decoding the data and supplying a result of the decoding as an analogsignal back to the monitor apparatus 1. The monitor apparatus 1 is thencapable of automatically outputting the analog signal representing thedesired digital data as a video display on the screen G of the displayunit employed in the monitor apparatus 1 as shown in FIG. 13A.

In addition, by creating a content information table in advance asdescribed above, the message, which was displayed when a content wasreceived as undecodable digital data, can be displayed, being superposedon the video display of the content received as an analog signalresulting from a process of decoding the digital data in an externalapparatus as shown in FIG. 13B. With the message displayed on the screenas shown in this figure, the user is capable of knowing the sourceapparatus originally generating the content. In this example, the sourceapparatus originally generating the content is an external apparatuswith a source apparatus ID of 1.

In the case of the network shown in FIG. 1, for example, a digitalcontent generated by the DV storage 2 is rerouted to the DV camcoder 4to be decoded thereby, being converted into an analog signal which iseventually-re-supplied to the monitor apparatus 1. In this way, the useris capable of watching and listening to a digital content generated bythe DV storage 2 and initially supplied to the monitor apparatus 1 as aDV signal, which cannot be decoded by the monitor apparatus 1.

Thereby, the user of the monitor apparatus 1 is capable of watching andlistening to video and audio outputs of a desired digital content playedback by an external apparatus without the need to carry out a difficultoperation on the monitor apparatus 1. As a result, a user not familiarwith the monitor apparatus 1 or the external apparatuses connected tothe monitor apparatus 1 by the network is capable of reliably watchingand listening to a digital content played back and output by any one ofthe external apparatuses.

It should be noted that the judgment formed at the step S202 does nothave to be based on format information extracted from the FMT field ofthe header of an isochronous packet. As described earlier, for example,digital data received by the IEEE 1394 I/F circuit 14 is decoded, and aresult of the decoding can be used as a basis for forming a judgment asto whether or not the received digital data has been compressed andencoded by adoption of a method that makes it impossible for the monitorapparatus 1 to decompress and decode the data. That is to say, there area variety of ways to form a judgment as to whether or not the receiveddigital data has been compressed and encoded by adoption of a methodthat makes it impossible for the monitor apparatus 1 to decompress anddecode the data.

As described earlier, the monitor apparatus 1 has the analog inputterminals other than the terminals for the IEEE 1394 I/F circuit 14. Itshould be noted, however, that it is not always necessary to provide themonitor apparatus 1 with analog input terminals other than terminals forthe IEEE 1394 I/F circuit 14. For example, in place of an analog inputterminal, it is also possible to provide a digital input terminal forreceiving an already decompressed base-band signal. With such a digitalinput terminal, the monitor apparatus 1 is capable of receiving analready decompressed base-band signal.

Since the base-band signal supplied to the digital input terminal hasalready been decompressed, it is not necessary for the monitor apparatus1 to decompress or decode the signal. Instead, the base-band signalreceived by the monitor apparatus 1 is supplied to a D/A converter forproducing a normally usable signal. To put it concretely, in place ofthe analog input terminals S1, S2 and S3, it is possible to providedigital input terminals each used for receiving an already decompressedbase-band signal. Thus, the present invention can also be applied to acase wherein a base-band signal received from an external apparatusconnected to the monitor apparatus 1 by the network is subjected to D/Aconversion before being supplied to the superposition circuit 19.

That is to say, the present invention can be applied to not only a casewherein digital data encoded by adoption of some methods including acompressing and encoding method is not supplied to the monitor apparatus1 as it is, but the digital data is subjected to decoding and D/Aconversion in an external apparatus to generate an analog signal usablein the monitor apparatus 1 to supply thereto, but also a case wherein ausable analog signal is supplied to the monitor apparatus 1 as it iswithout being subjected to D/A conversion as described above.

It should be noted that, in the monitor apparatus 1 implemented by thisembodiment, digital data decoded in the MPEG decoder 17 by adoption ofthe MPEG decoding method is subjected to D/A conversion in thesuperposition circuit 19.

In addition, while a route for supplying a content is automaticallyselected in the embodiment described above, the scope of the presentinvention is not limited to such a scheme. In an operation to dub adigital content in the network to which the monitor apparatus 1 isconnected, for example, an external apparatus capable of copying thedigital data generated by a desired source apparatus in a compressedstate as it is is determined.

Then, a command is issued to the determined external apparatus toreceive and copy the digital content generated by the desired sourceapparatus and, at the same time, a command is given to the sourceapparatus to output the digital data to the copying external apparatus.By issuing such commands, the external apparatus capable of copying thedigital data generated by the desired source apparatus in a compressedstate as it is automatically and normally copies and stores the data.

It should be noted that, in the embodiment described above, displayedinformation is not limited to a transmission channel, a source apparatusID and format information. By displaying also information on a digitalcontent received from a digital bus, information on a content receivedthrough an analog input terminal, information on whether or not digitaldata has been encrypted and the like, it is possible to clearly show thecontent supply route and the original condition of the content. Thevarious kinds of information displayed are effective for identifying anexternal apparatus capable of copying data.

In addition, the monitor apparatus 1 implemented by the embodimentdescribed above has a function, which is used for displaying pieces ofinformation on a digital content supplied to the monitor apparatus 1such as a transmission channel number (or an isochronous channelnumber), a source apparatus ID and format information as shown in FIG. 6in case the monitor apparatus 1 is not capable of decoding the digitalcontent. The monitor apparatus 1 also has a function to create a contentinformation table, display part or all of the table and transmit part orall of the table to an external apparatus at a request made by theexternal apparatus. Furthermore, the monitor apparatus 1 also has anautomatic select function for automatically selecting a content supplyroute.

However, it is also possible to provide a monitor apparatus having onlythe function, which is used for displaying pieces of information on adigital content supplied to the monitor apparatus 1 such as atransmission channel number (or an isochronous channel number), a sourceapparatus ID and format information in case the monitor apparatus 1 isnot capable of decoding the digital content.

By the same token, it is also possible to provide a monitor apparatushaving only the function to create a content information table, displaypart or all of the table and transmit part or all of the table to anexternal apparatus at a request made by the external apparatus.Likewise, it is also possible to provide a monitor apparatus having onlythe function for automatically selecting a content supply route.Similarly, it is also possible to provide a monitor apparatus havingonly any 2 of the 3 functions described above.

In addition, in the embodiment described above, information in the EMIfield of an isochronous packet is used as a basis for forming a judgmentas to whether or not incoming digital data has been encrypted. It shouldbe noted, however, that the scope of the present invention is notlimited to this scheme. For example, the level or another attribute ofdigital data supplied to the monitor apparatus 1 is detected todetermine whether or not the digital data has been encrypted. That is tosay, the formation of the judgment as to whether or not incoming digitaldata has been encrypted is based on the state of the digital data.

Furthermore, the embodiment described above is used for exemplifying anapplication of the present invention to a monitor apparatus. It is worthnoting, however, that the scope of the present invention is not limitedto a monitor apparatus. For example, the present invention can also beapplied to an apparatus called a set top box for receiving a digitalbroadcast, a digital VTR and other electronic equipment such as apersonal computer.

That is to say, the present invention can be applied to a variety ofinformation outputting apparatuses each used for receiving digital datathrough a digital interface provided therein, carrying out processingsuch as a decoding process on the digital data and outputting results ofthe processing.

Thus, the present invention can be applied to not only a case forhandling digital data comprising video and audio signals as describedabove, but also a case for handling other digital data such as computerprograms and computer data.

Moreover, the embodiment described above is used for exemplifying themonitor apparatus 1 provided with a digital interface conforming to theIEEE 1394 standard. It should be noted, however, that the scope of thepresent invention is not limited to such a digital interface. That is tosay, the present invention can also be applied to cases in which avariety of digital interfaces are employed for transmitting informationon main digital data (or a digital content) besides the main digitaldata itself.

In addition, while the embodiment described above uses 2 types ofcompressing and encoding method, namely, the DV method and the MPEG-TSmethod, the scope of the present invention is not limited to thesemethods. That is to say, the present invention can also be applied to acase in which digital data cannot be decoded due to other differences intransmission format. As described above, for example, there aredifferences in encoding method between the DV, MPEG, JPEG and othermethods, which result in the differences in transmission format. To putit concretely, the differences in transmission format include adifference in bit count per word and a difference in whether or notdigital data has been encoded and, in the case of a packet transmission,differences in packet size, header size and header fields.

In the case of the digital television broadcasting, for example, adigital content may be broadcasted by adoption of typically a signaltransmission method known in the US as a DSS method in addition to theMPEG-TS signal format. Furthermore, the DSS method can be an SD(standard definition) method or an HD (high definition) method. Areceiver compatible with the DSS method may conceivably be capable ofdecoding digital data conforming to the SD method but not capable ofdecoding digital data conforming to the HD method. In a word, thepresent invention can also be applied to a system in which digitalcontents transmitted by digital broadcasting are encoded in accordancewith different encoding methods and, hence, have different transmissionformats.

That is to say, when the monitor apparatus 1 is not capable of decodinga broadcasted signal received from a digital television broadcastingstation, the monitor apparatus 1 is capable of displaying the broadcastchannel number, information on the format and other attributes of thedigital television broadcasting. In this case, information extractablefrom the incoming broadcast signal is displayed. For example,information on a digital broadcast signal transmitted through abroadcasting channel is prepared in advance for each broadcastingchannel in an electronic apparatus having a function for receiving thedigital broadcast signal to be displayed and reported to the user.

1. An information-outputting apparatus connected to a network comprisinga plurality of electronic apparatuses, said information-outputtingapparatus comprising: a digital interface unit for receiving a digitalsignal having a predetermined format; signal-decoding means for decodingthe digital signal; decodable/undecodable judgment means for forming ajudgment as to whether or not the digital signal received by saiddigital interface unit can be decoded by said signal-decoding means; andinformation-reporting means for reporting a source-apparatus informationindicating an electronic apparatus serving as a source outputting saiddigital signal and an information on the predetermined format, whereinsaid information-reporting means further reports that the digital signalreceived by said digital interface unit is undecodable to a user bydisplaying said report on a display unit in case an outcome of ajudgment formed by said decodable/undecodable judgment means indicatesthat said digital signal is undecodable.
 2. An information-outputtingapparatus according to claim 1, said apparatus further havinginformation-tabularizing means for organizing source-apparatusinformation and information on a format, which are detected by saidinformation-detecting means, for each of said electronic apparatusesconnected to said network in a table by associating a pair ofsource-apparatus information and information on a format with saidcorresponding electronic apparatus, wherein said information-reportingmeans reports said information tabularized by saidinformation-tabularizing means to the user.
 3. An information-outputtingapparatus according to claim 2, said apparatus having: one or morebase-band-signal input terminals each connected to one of saidelectronic apparatuses connected to said network and used for receivinga base-band signal generated by said electronic apparatus; andinformation-adding means for adding source-apparatus informationindicating a source apparatus generating a base-band signal andinformation, which indicates a format of said base-band signal in casesaid base-band signal has been encoded, for each of said electronicapparatuses connected to said base-band-signal input terminals to saidinformation tabularized by said information-tabularizing means byassociating said source-apparatus information with said informationindicating a format.
 4. An information-outputting apparatus according toclaim 2, said apparatus having apparatus-pointing means for pointing outa source apparatus generating a signal presently displayed on a screenin said tabularized information.
 5. An information-outputting apparatusaccording to claim 1, wherein said decodable/undecodable judgment meansforms a judgment as to whether a digital signal received by said digitalinterface unit is decodable or undecodable on the basis of saidinformation on a format detected by said information-detecting means. 6.An information-outputting apparatus according to claim 1, wherein saidinformation-reporting means further outputs information as a sound or avoice generated by speakers.
 7. An information-outputting apparatusaccording to claim 1, said information-outputting apparatus furtherhaving encrypted/unencrypted judgment means for forming a judgment as towhether or not a digital signal received by said digital interface unithas been encrypted, wherein said information-reporting means reports aresult of said judgment formed by said encrypted/unencrypted judgmentmeans to the user.
 8. An information-outputting apparatus according toclaim 7, wherein: said information-detecting means is also capable ofdetecting information indicating whether or not a digital signalreceived by said digital interface unit has been encrypted from saiddigital signal; and said encrypted/unencrypted judgment means forms ajudgment as to whether or not a digital signal received by said digitalinterface unit has been encrypted on the basis of said informationdetected by said information-detecting means to indicate whether or notsaid digital signal received by said digital interface unit has beenencrypted.
 9. An information-outputting apparatus according to claim 2,wherein any one of said electronic apparatuses connected to said networkis capable of arbitrarily making an access to said tabularizedinformation.
 10. An information-outputting apparatus according to claim1, wherein said digital buses are each a bus conforming to the IEEE 1394standard.
 11. An information-outputting apparatus according to claim 1,wherein said information on a format is information indicating anencoding method of a digital signal supplied by way of said digitalinterface unit.
 12. An information-outputting apparatus according toclaim 1, wherein said information on a format is information indicatinga transmission format of a digital signal supplied by way of saiddigital interface unit.
 13. An information-outputting apparatusaccording to claim 1, wherein said information-reporting means reports apredetermined message in addition to said source-apparatus informationand said information on a format to the user.
 14. Aninformation-outputting apparatus according to claim 1, wherein, aftersaid information-reporting means reports said source-apparatusinformation and said information on a format to the user for apredetermined period of time, reporting is ended.